1. Field of the Invention
This invention pertains to the field of radiation, physics and pharology. More particularly, this invention pertains to an all-weather, signal system employing long wavelength coherent radiation. In still greater particularity, this invention concerns a portable optical signal by which a navigational beam and identification may be transmitted to remote observation points. By way of further characterization, but without limitation thereto, this invention will be described as it pertains to a infra-red signal to be used by ground forces to communicate with airplanes employing infra-red sensors.
2. Description of the Prior Art
In modern warfare it is essential that operational personnel of fast flying aircraft be able to locate friendly ground forces and other navigational points with a minimum of time and in a variety of weather conditions. Previous methods for achieving this identification employed the use of marker panels and flares.
Marker panels, although satisfactory in daytime operation, are limited by the visibility conditions and the time for identification.
Flares although capable of nighttime performance, sacrifice covert operation and therefor permit detection of the forces by hostile troops in the area.
Other prior art systems have used chemical fluorescence but such systems depend upon an active source within the approaching aircraft and may be obscured by vegetation and other ground objects such that their efficiency is largely limited to use in an water environment. Additionally, such systems require the use of chemicals which may be dangerous to personnel, and animal and plant life in the vicinity.
Although prior art systems using active illumination by the ground forces to indicate their position to approaching aircraft are known, these systems rely on inefficient light sources which require heavy power supplies and frequently have wavelengths which are diffused and absorbed by smoke, haze, clouds and other atmospheric foreign particles.